Hm, i don't have any experiences with this specific cooler neither with the Gigabyte, but be sure that MSI coolers are great, and yes, they give extended warranty because they use more expensive components and a better cooling solution certainly it will hardly gives you headaches.
I just bought a MSI 6770 and i was very close to getting the gigabyte 6770 which was cheaper but im glad i didnt there were some bad reviews i read something to do with crossfire not working. Im sure both would be good but ive heard better things about MSI and im loving the one i just bought.